Surveyor 7 (January 1968) was a scientific mission and its TV registered 2 lasers aimed at the spacecraft from observatories in California & Arizona. I have seen a reproduction of that photo, but the 'laser' specks on the night side of Earth appeared to be retouched onto the photo in the version I saw. Is there an original image of this experiment in existance showing their actual brightnesses?

Don

I have image of laser beam created by me from the matrix (60 x 60 ? ) of original data.

Surveyor 7 (January 1968) was a scientific mission and its TV registered 2 lasers aimed at the spacecraft from observatories in California & Arizona. I have seen a reproduction of that photo, but the 'laser' specks on the night side of Earth appeared to be retouched onto the photo in the version I saw. Is there an original image of this experiment in existance showing their actual brightnesses?

Printout of the region around the laser spot of the digitized picture.The number at each point represents the optical density, on a scaleof 64 gray levels (0 = white, 63 = black). The laser spot is completelysaturated at two point in the picture.

Original image (not very spectacular)laser_beam5.bmp ( 363.05K )
Number of downloads: 419

The only printed version I can remember seeing was in "Exploring Space with a Camera"-snip- is this where you saw it?[/quote]

Yes, among others. In 'Exploring Space...' page 80, examining the reproduction on the printed page closely reveals apparent touch up marks, undoubtedly assisting in the presentation of real data but perhaps overly so. Four short vertical marks appear to have been applied to a 'master print' replicated for mass reproduction. One of the marks shows variance from the vertical scan line orientation, and one of them is drawn so as to spill over into the dark gap between the scan lines. What did the reproduction in the Surveyor 7 science report look like? The National Geographic book 'Man's Conquest of Space' by William R. Shelton, page 134 bears a smaller reproduction of the same photo, with the right hand beam spot further accentuated by extending the rightmost short line. I can't open the .bmp file on my Mac so I would appreciate seeing the raw data at last!

The Surveyor images of the crescent (i think) earth with the laser spots were 600 line analog images. The normal data product was slow-scanned directly onto negative film in a data-recording camera.

On rare occassion, the analog data tapes were played back and digitized for quantitative analysis but these weren't. Images were also scan-converted in not-quite-real time for TV display, as during the Surveyor 1 landing TV coverage.

The Laser experiment image clearly showed lines of a raster image with darker gaps between the lines, the laser spots were very sharp brightness increases on a couple lines, extending across what in digital data would be about 3 pixels along the line.

There were more lasers involved in the test than the two in the image, but cloudy conditions at the telescope sites obliterated any chance of them showing up.

I wonder if a carefully pointed 5 watt green laser would be as visible from the Moon as the lasers used then. There are enough such lasers that a letter or symbol could be arranged for the benefit of future lunar telephoto camaras. It is also just possible, primarily through the strong Lunar 'back scattering', that a determined mass effort could 'illuminate' the Lunar night side using the thousands of existing brighter than 5mw green lasers carefully pointed at the Moon. An early attempt at this using inferior red lasers of several years ago can be read of here:

Photo for April 2008: Mariner IV flyby of Mars:In November 1964, NASA had 2 Mariner spacecraft ready for a Mars flyby mission. However, the shroud (fairing) on the Mariner III launch vehicle failed and engineers had to rework the Atlas-Agena shroud urgently in order to launch Mariner IV within the Mars-window. The 260 kg Mariner IV was launched on 28th November 1964 and flew by Mars in July 1965, beaming 22 b&w photos back to the Jet Propulsion Laboratory.In October 1967, Mariner IV was used for attitude-control tests in support of Mariner V, its twin spacecraft which was modified for a Venus flyby (closest October 1967). Final communications with Mariner IV took place on 21st December 1967…

http://ntrs.nasa.gov turns up several hits on "Surveyor 7 laser". There is a tech report by Jim Brault and S.K. Poultney on the laser illumination experiment (alas not available electronically). Part 2 of the Surveyor 7 Science Report is here as a scanned PDF. (Or maybe not - my PC reports that the file is corrupted, and loading it actually crashes Safari on a Mac. I reported the problem...)

Update an hour later - the file isn't corrupted, it's just 567 Mbytes and upsets these browsers. There is much detail about the laser collimating and pointing systems and observing sessions. A full-page image reproduction has been scanned at such a contrast the I don't see either laser at all.

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